This invention relates to yarn winders and a method of operating the same, and more particularly to a yarn winder provided with means for transferring yarn from a nearly fully wound package on a bobbin mounted on a first chuck to an empty bobbin mounted on a second chuck, and to a method of effecting such transfer.
As mentioned in copending application Ser. No. 809,676, modern winders, for winding yarn into yarn packages on bobbins or tubes, generally include two or more rotatable chucks, each supporting one or more bobbins or tubes. While one chuck is being rotated for winding of yarn into packages on bobbins or tubes mounted thereon, empty bobbins or tubes are placed on a second chuck then in a standby condition. When full packages have been wound on the first chuck, the latter is brought to a stop and the full packages are removed therefrom. It is then necessary for the winder operator or attendant to properly thread the yarn for winding on the bobbins or tubes on the second chuck.
The threading of the yarn is usually effected by feeding the end of the yarn into an aspirator or the like, and then using a "doffer" to engage the yarn in transverse guides for proper winding in a criss-cross manner on the bobbins or tubes. Such re-threading or re-guiding of the yarn, when full packages have been wound so that the yarn can begin to be wound on empty bobbins or tubes, requires a considerable amount of time. More important, however, is the waste involved, particularly when yarns are being fed at very high speeds. Additionally, it is difficult, with known winders, to obtain accurately sized packages as well as uniform packages.
The changeover time required for switching yarn from a full package to an empty bobbin or tube is of particularly great importance with the heavy denier yarns now being used to an increasing extent. It is important that the changeover time be kept to a minimum, an the magnitude of the changeover time is in direct relation to the amount of yarn wasted during transfer from a full package to an empty bobbin or tube. The foregoing factors are becoming of increasing importance with the development of winders using pairs of top and bottom chucks on opposite sides of a traverse housing, with each chuck accomodating two or more tubes or bobbins. While such winders increase the efficiency of the yarn winding operation, the increase in efficiency is hampered by the time required to transfer from a full bobbin or package to an empty bobbin or tube. In some of the more modern winders, used with heavier denier yarn, the speed of yarn feed is so fast that it is necessary to make a transfer from a full package to an empty bobbin or tube substantially every ten minutes. This involves relatively high labor costs due to the number of personnel required.
The problem of providing a mechanism for automatically transferring yarn from a full package to an empty bobbin or tube for winding on the latter, without manual assistance, is effectively solved by the mechanism and method of application Ser. No. 809,676. With this method and mechanism, the operation of transferring the yarn is much more accurate from the standpoint of package size and much more uniform, in addition to which the waste is reduced to a minimum, but tolerable, amount.
However, it has been found, in practice, that the mechanism and method of application Ser. No. 809,676, with respect to the yarn transfer operation, can be improved in several respects, while using the same principle but requiring fewer parts, obtaining more "wrap around" the chuck by the yarn to be transferred, a more rugged construction, and with less possibility of pneumatic actuators moving yarn transfer rods at the wrong time due to failure of pneumatic components.
For example, with the method and mechanism of application Ser. No. 809,676, it was not possible to obtain enough "wrap around" the empty bobbin at transfer, thus causing some failures in picking up and clamping of the yarn by the hook and clamp on the chuck, and to improve this operation would require more space than is available. Thus, in the apparatus of application Ser. No. 809,676, an additional cylinder and slide component would have to be added to the top chuck mechanism to attain more "wrap around" and this would increase the possiblity for pneumatic failure. Also, with the method and mechanism of application Ser. No. 809,676, there was the possiblity that a malfunction or pneumatic failure could force the extension cylinder to push the transfer rod against the drive roll with resultant possible damage to components. Some of the possible disadvantages of the method and mechanism of application Ser. No. 809,676 result from the fact that the yarn transfer rods are pivoted about the axes of the respective chucks, and also due to the fact that the nearly fully wound yarn package is not positively rotated during the transfer operation, which resulted in some loss of tension in the yarn loop being drawn by the transfer rods.